The present invention relates to a safety mechanism including hand restraint safety mechanism for use by an operator of a machine having moving machine elements.
Heretofore, various types of hand restraining apparatus of the type to which the present invention relates have been used to remove the machine operator's hands from the path of travel of moving machine elements. In one type of prior hand restraint apparatus, the operator's hands are removed from the danger area as the machine operates. Thus, the operator's hands can still be in the danger area as the machine elements begin to move. A hand restraining safety apparatus which eliminates the above situation by preventing the machine from cycling until the operator's hands are in a safety position remote from the machine is disclosed in copending application of the same inventor for Safety Mechanism for Special Machines and Fixtures, Ser. No. 351,516, filed Apr. 16, 1973 now U.S. Pat. No. 3,847,259. In certain respects the present invention represents an improvement upon the safety apparatus of that earlier filed application.
Accordingly, one important objective of the present invention is to provide a safety mechanism for use by a machine operator wherein not only is movement of elements on the machine prevented until the operator's hands are disposed in a safety position remote from the machine, but also a mechanical safety interlock remains interposed between relatively movable machine elements until the operator's hands are in the safety position. Only after the safety mechanism displaces the operator's hands to the safety position is the mechanical interlock removed and then only with both the mechanical interlock removed and the operator's hands in the safety position is the machine stroked. At the conclusion of the machine stroke the mechanical interlock is reestablished before the hand restraints are released. Hence, a further object of the invention is to provide increased operator safety for the operators of various types of machines such as presses, special machines and fixtures.
The particular details of the present invention by which the foregoing objects are attained include a novel pneumatic control circuit having failsafe valve means operatively associated therewith to sense operating positions of various moving elements of the safety mechanism and the machine with which it is in use. Each failsafe valve means can pass a fluidic signal only when the element whose position is to be sensed is the intended position. By virtue of the unique arrangement of these failsafe valve means in pneumatic circuit, proper sequential operation of the various elements is always assured thereby providing maximum operator safety. In the preferred embodiment of the invention disclosed herein, the particular details of the novel pneumatic control circuit constitute further inventive features of the present disclosure.
One especially important improvement of the present invention involves a novel non-repeat circuit for the safety mechanism which prevents the safety mechanism from being repeatedly operated and the machine from being repeatedly stroked so long as the actuating element for initiating a machine cycle is held in the actuating position. Because of this beneficial feature, accidental cycling, and hence loss of production time, is eliminated.
The foregoing objects and features of the invention along with additional features, advantages and benefits of the invention will be seen in the ensuing description and claims which are to be taken in conjunction with the accompanying drawings. The drawings illustrate a preferred embodiment of the invention in accordance with the best mode presently contemplated for carrying out the invention.